Managing soil denitrification

ABSTRACT:

Denitrification of nitrate in the soil can be a mechanism of significant loss of fertilizer and soil nitrogen, but it can also serve to remove excess NO₃ that is leached below the root zone. Inappropriate management of irrigation water and fertilizer N in irrigated corn has resulted in leaching of excess N from the rooting zone and contamination of groundwater and also has contributed to the increasing concentration of N₂O in the atmosphere. Denitrification can be both microbial and chemical, but the microbial process dominates in most soils through a stepwise reduction of NO₃ to N₂. Soil atmosphere O₂ concentration, which is regulated by soil water content interactively with soil texture and microbial respiration, is the main controller of the process. The oxygen consumption rate depends on the amount of easily degradable organic C compounds and the interplay of water and carbon in developing in the soil reduced oxic conditions, which regulate not only the amount of total denitrification but also the ratio of N₂O to N₂ produced. Appropriate management of nutrient input, relative to crop demand and soil water status, can limit nitrogen loss from denitrification. This paper describes the role of denitrification in the nitrogen economy of crop production and the environment, describes the process involved, and presents suggestions for limiting N loss caused by denitrification.